1. Field of the Invention
The present invention relates to a resist composition which has high .gamma.-value and high film thickness retention.
2. Description of the Related Art
A composition containing a compound having a quinone diazide group such as a naphthoquinone diazide group, a benzoquinone diazide group, etc. and an alkali-soluble resin finds use as a positive resist, because upon exposure to ultraviolet rays, the quinone diazide group decomposes to form a carboxyl group whereby the originally alkali-insoluble composition becomes alkali-soluble. A condensation product of a phenol compound (e.g. trihydroxybenzophenone, tetrahydroxybenzophenone and so on) with a quinone diazide compound is used as a sensitizer.
However, particularly with integrated circuits, miniaturization has proceeded with a rise in the integration level, which results in demands for formation of patterns of submicron order and more excellent resolution (high .gamma.-value). As a result, the conventional compositions cannot improve the .gamma.-value to the desired level.
For example, if the amount of quinone diazide group is increased to improve the .gamma.-value, serious problems such as deterioration of sensitivity and increase of residues after developing arise.
Therefore, the improvement of the .gamma.-value is limited.
To achieve better resolution, high film thickness retention as well as the high .gamma.-value is desired.